Polymeric External Gear Pump for Hot Cooking Oil

ABSTRACT

An overhung external spur gear positive displacement pump for hot oil or deep fryer applications is disclosed. The external gear pump includes a thermoplastic casing that includes a through bore for accommodating a drive shaft that leads to a pump chamber that accommodates a drive gear and a driven gear. The thermoplastic casing is connected to a stationary pin. The thermoplastic casing also includes a proximal end coupled to a motor and a distal end coupled to a thermoplastic head. The gears are enclosed in the pump chamber by the thermoplastic head. The stationary pin is accommodated within the driven gear and the drive shaft is coupled to the drive gear. The thermoplastic head is provided in the form of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the thermoplastic casing.

TECHNICAL FIELD

This disclosure relates to pumps for cooking oil and, more specifically, to pumps used to deliver and re-circulate oil in a deep fryer. Still more specifically, this disclosure relates to improved and more economical design for pumps intended to deliver cooking oils. The disclosed pump designs are fabricated from engineered thermoplastic, require no bearings for supporting the drive shaft and feature a flat head plate that does not require precision alignment with the casing.

BACKGROUND

Deep fryers are a necessity of the food service industry and particularly for the fast food service industry. Deep fryers use a substantial amount of shortening or oil during the cooking process. During the cooking process much of the oil is absorbed by a food product, resulting in loss of oil volume. The remaining oil can become filled with debris such as burned food particles that adversely affect the taste of food cooked in used cooking oil. Accordingly, there is a need for a deep fryer that efficiently filters used oil, which requires reliable pumps to circulate the used oil through a filtering system.

A typical deep fryer typically includes a filter/return pump for drawing used cooking oil from the cooking vat through a filter system and then pumping the filtered oil back into the cooking vat. Further, many deep fryers include multiple cooking vats. As a result, the distribution system to direct the flow from the filter/return and supply pumps to the various cooking vats of a typical deep fryer may be complex and requires at least one reliable pump for the filter and return functions.

Typical pumps used with deep fryers are gear pumps, specifically external gear pumps that include one drive gear mounted on a drive shaft and that is enmeshed with a driven gear mounted on a driven shaft. An example of such a pump is illustrated in FIG. 1. The pump 10 includes a casing 11 (also known as a bracket) which features a through bore 12 which accommodates the drive shaft 13 and which passes through the pump chamber 14. The pump chamber 14 is connected to a recess 15 which accommodates the driven shaft 16. The drive shaft 13 is coupled to a drive gear 17 and the driven shaft 16 is coupled to a driven gear 18. Both the drive shaft 13 and driven shaft 16 extend out of the pump chamber 14 and into the head 21 (also known as a head plate). To accommodate the drive shaft 13 and driven shaft 16, the head 21 includes a pair of recesses 22, 23 which accommodates the distal ends 24, 25 of the drive and driven shafts 13, 16 respectively. The drive and driven shafts 13, 16 are supported at both their respective distal ends 24, 25 and proximal ends 26, 27 by needle bearings 28. The head 21 is coupled to the casing 11 by a plurality of cap screws 29 which pass through alignment sleeves 32 that ensure proper alignment between the head 21 and casing 11. The combination of the casing 11 and head 21 is also referred to as a housing. The head 21 also includes a slot or groove for accommodating an o-ring 33.

As seen from FIG. 1, the need to support the distal ends 24, 25 of the drive and driven shafts 13, 16 at the head 21 and the requirement for an exact alignment between the head 21 and the casing 11 requires substantial machining costs for both the casing 11 and the head 21 along with the use for cap screws 29, alignment sleeves 32 and dowel pins. In order to reduce the amount of labor and machining, changes to the existing external gear pump designs will be needed.

Further, currently available pumps, used for use in food manufacturing and in food preparation, are prone to frequent seal failure when used to pump natural, unsaturated and trans-fat-free oils such as corn, soybean and canola oils. For example, pumps are used in hot oil filtration process of deep fryers used in the manufacturing or preparation of French fries, fish, and chicken. During the transition between trans-fat oils and zero trans-fat oils, it has been found that seal failure has become commonplace. Accordingly, an improved seal design and improved access to seals used in pumps intended for pumping hot trans-fat-free oils is needed so that conventional seals such as that shown at 32 in FIG. 1 made from fluoropolymer elastomers or fluoroelastomers may be replaced with materials that have better wear characteristics in the presence of trans-fat-free oils.

Fluoroelastomers are commonly used in O-rings and other molded or extruded goods. Fluoroelastomers are part of a family comprising copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) as well as perfluoromethylvinylether (PMVE) containing specialties. The fluorine content of the most common fluoroelastomers varies between 66 and 70%. As noted above, the failure rate of fluoroelastomer seals in pumps used to pump zero trans-fat oils is unacceptably high.

The fluoroelastomer lip seals like that shown at 32 in FIG. 1 are failing in a timeframe as little as six months when used with zero trans-fat oils. The failure is due to tearing of the fluoroelastomer material as the oil “varnishes” out onto the drive shaft 13 thereby causing the seal to stick and then abrade away in a short period of time. Therefore, new pumps and new seals for use in pumps are needed for reliably pumping zero trans-fat oils.

As shown in FIG. 1, prior art gear pump casings and heads have been fabricated from metallic materials in order to maintain an exacting tolerance between the idler or driven gear 18 and the drive gear 17. In this regard, the metallic gear pump casing 11 and head 21 are machined to a size which maintains a seal against the drive gear and idler gear as required for proper operation. However, metallic gear pump casings are expensive to manufacture due to the time and effort required to machine the gear pump casings and metallic heads to the correct dimensions. Additionally, metallic gear pump casings and heads are heavy and difficult to work with. Therefore, there is presently a need for a gear pump casing and head which are inexpensive to fabricate and easier to assemble into a complete gear pump.

SUMMARY OF THE DISCLOSURE

The above-mentioned deficiencies in prior art gear pump casings and heads is alleviated by providing a thermoplastic gear pump casing and a thermoplastic head which are formed from an engineered thermoplastic material. In this respect, the casing and head are easy to manufacture and handle. Additionally, a method of forming a plastic gear pump casing and head is disclosed which maintains the tolerances needed for proper operation.

In one example, an external gear pump is disclosed that comprises a thermoplastic casing that comprises a through bore for accommodating a drive shaft that leads to a pump chamber that accommodates a drive gear and a driven gear. The casing is connected a stationary pin. The casing further comprises a proximal end coupled to a motor and a distal end coupled to a thermoplastic head. The gears are enclosed in the pump chamber by the thermoplastic head. The stationary pin is accommodated within the driven gear and the drive shaft is coupled to the drive gear. The thermoplastic head consists essentially of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the casing and the casing to another component, such as a prime mover or motor.

In a refinement, the fasteners are cap screws.

In a refinement, the through bore of the thermoplastic casing includes no bearings that engage the drive shaft.

In a refinement, the through bore of the thermoplastic casing and the drive shaft are sized so the through bore supports and provides a bearing function for the drive shaft without the use of an additional bearing or bearings.

In a refinement, the through bore comprises a distal end connected to the pump chamber and a proximal end connected to the proximal end of the thermoplastic casing. The proximal end of the through bore is recessed to accommodate a seal through which the drive shaft passes.

In a refinement, the distal end of the thermoplastic casing comprises a groove that encircles the pump chamber for accommodating a seal that is sandwiched between the distal end of the thermoplastic casing and the thermoplastic head.

In another example, a deep fryer pump is disclosed which comprises a casing that comprises a through bore for accommodating a drive shaft and a pump chamber for accommodating a drive gear and a driven gear. The thermoplastic casing further is connected to a stationary pin, preferably by molding the pin into the casing. However, other means for coupling the casing to the stationary pin will be apparent to those skilled in the art. The thermoplastic casing further comprises a proximal end coupled to a motor and a distal end coupled to a thermoplastic head. The gears are enclosed in the pump chamber by the thermoplastic head. The stationary pin is accommodated within the driven gear and the drive shaft is coupled to the drive gear. The thermoplastic head consists essentially of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the thermoplastic casing and the thermoplastic casing to another component, such as a prime mover.

In another example, a deep fryer pump is disclosed that consists essentially of a thermoplastic casing that consists essentially of a through bore for accommodating a drive shaft, a pump chamber for accommodating a drive gear and a driven gear and a recess connected to the pump chamber for accommodating a stationary pin. Further, a proximal end of the thermoplastic casing is coupled to a motor and a distal end of the thermoplastic casing coupled to a thermoplastic head. The thermoplastic casing also consists essentially of a groove that encircles the pump chamber for accommodating a seal that is sandwiched between the distal end of the thermoplastic casing and the thermoplastic head. The gears are enclosed in the pump chamber by the thermoplastic head. The stationary pin is accommodated within the driven gear and the drive shaft is coupled to the drive gear. The thermoplastic head consists essentially of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the thermoplastic casing and that couple the thermoplastic casing to another component, such as a prime mover. And, the through bore comprises a distal end connected to the pump chamber and a proximal end connected to the proximal end of the thermoplastic casing. The proximal end of the through bore being recessed to accommodate a seal through which the drive shaft passes.

In a refinement, the disclosed pumps are listed for use as a deep fryer oil pump by NSF.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a prior art external gear pump.

FIG. 2 is a side sectional view of a disclosed external gear pump.

FIG. 3 is an end view of the external gear pump shown in FIG. 2, particularly illustrating the thermoplastic head.

FIG. 4 is in view of the external gear pump shown in FIGS. 2 and 3, particularly illustrating the proximal end of the thermoplastic casing and drive shaft.

FIG. 5 is a side view of the external gear pump shown in FIGS. 2-4, particularly illustrating an inlet or outlet port.

DETAILED DESCRIPTION

Referring to FIG. 2, a disclosed pump 100 is shown in a side sectional view. The pump 100 includes a thermoplastic casing 111 that includes a proximal end 119 and a distal end 120. The distal end 120 of the thermoplastic casing 111 is coupled to a thermoplastic head 121 that is provided in the form of a plate that is flat on a proximal side 139 that faces the thermoplastic casing 111 and includes structurally reinforcing ribs 138 on a distal side 137 of the head 121. An o-ring 133 provides a seal between the thermoplastic head 121 and casing 111, but the groove or slot 130, which accommodates the o-ring 133, is disposed in the distal end 120 of the thermoplastic casing 111 as opposed to the thermoplastic head 121.

The thermoplastic casing 111 includes a through bore 112 which accommodates the drive shaft 113. The drive shaft 113 has a proximal end 126 which includes a coupling 120 for connecting the drive shaft 113 to a motor (not shown). The proximal end 126 of the drive shaft 113 is also disposed within a recess 131 in the thermoplastic casing 111 which accommodates a lip seal 132. The drive shaft 113 also includes a distal end 124 that is disposed within the pump chamber 114 and not within the thermoplastic head 121. The through bore 112 leads to the pump chamber 114 which, in turn, leads to the stationary pin 116 that may be molded into the casing 111. The drive shaft 113 is coupled to the drive gears 117 and the stationary pin 116 is axially received in the driven or idler gear 118 so the driven gear 118 can rotate about the stationary pin 116. The through bore 112 that accommodates the drive shaft 113 is sized so it can serve as a journal bearing surface for the drive shaft 113. The reader will note that the pump 100 includes no additional bearings for supporting the drive shaft 113. The design shown in FIG. 2 can be referred to as an over hung design or the pump 100 can be referred to as an over hung external spur gear positive displacement pump. The driven gear 118 rotates about the stationary pin 116. Therefore, the stationary pin 116 requires no bearing support.

The thermoplastic head 121 is coupled to the thermoplastic casing 111 with cap screws 129 that are threaded into the threaded inserts 115 that may be molded into the casing. The thermoplastic casing 111 may be coupled to another component, such as a prime mover 130 by using cap screws 229 that pass through the casing 111. Alignment sleeves, like those shown at 34 in FIG. 1, are not necessary. The needle bearings 28 of FIG. 1 are also not necessary.

End views and a side view are shown in FIGS. 3-5 respectively. In FIG. 3, the thermoplastic head 121 is shown attached to the thermoplastic casing 111 with a pair of cap screws 129 or other simple fasteners. Dowel pins are not required for the openings 135 as the openings 135 may be used in combination with longer cap screws 229 to couple the pump 100 to another component, such as a prime mover 230, as shown schematically in FIG. 2. Similarly, openings 136 are shown on the proximal end 119 of the thermoplastic casing 111, which may be used to couple the pump 100 to another component.

By adapting the design illustrated in FIGS. 2-5, a simplified design for the thermoplastic head 121 is provided, the required machining is reduced for the thermoplastic casing 111 and both the needle bearings 28 and alignment sleeves 32 are eliminated.

INDUSTRIAL APPLICABILITY

The disclosed overhung external spur gear positive displacement pump 100 is suitable for pumping hot cooking oil for deep fryer applications and has been listed for use as a deep fryer oil pump by NSF. 

1. An external gear pump comprising: a thermoplastic casing comprising a through bore for accommodating a drive shaft that leads to a pump chamber for accommodating a drive gear and a driven gear, the thermoplastic casing being coupled a stationary pin, the thermoplastic casing further comprising a proximal end coupled to a motor and a distal end coupled to a thermoplastic head, the gears enclosed in the pump chamber by the thermoplastic head, the stationary pin coupled to the driven gear, the drive shaft coupled to the drive gear, the thermoplastic head consisting essentially of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the thermoplastic casing.
 2. The pump of claim 1 wherein the fasteners are cap screws.
 3. The pump of claim 1 wherein the through bore of the thermoplastic casing includes no bearings that engage the drive shaft.
 4. The pump of claim 1 wherein the through bore of the thermoplastic casing and the drive shaft are sized so the through bore supports and provides a bearing function for the drive shaft without the use of an additional bearing.
 5. The pump of claim 1 wherein the through bore comprises a distal end connected to the pump chamber and a proximal end connected to the proximal end of the thermoplastic casing, the proximal end of the through bore being recessed to accommodate a seal through which the drive shaft passes.
 6. The pump of claim 1 wherein the distal end of the thermoplastic casing comprises a groove that encircles the pump chamber for accommodating a seal that is sandwiched between the distal end of the thermoplastic casing and the thermoplastic head.
 7. A deep fryer pump, the pump comprising: a thermoplastic casing comprising a through bore for accommodating a drive shaft and a pump chamber for accommodating a drive gear and a driven gear, the thermoplastic casing being coupled to a stationary pin, the thermoplastic casing further comprising a proximal end coupled to a motor and a distal end coupled to a thermoplastic head, the gears enclosed in the pump chamber by the thermoplastic head, the stationary pin coupled to the driven gear, the drive shaft coupled to the drive gear, the thermoplastic head consisting essentially of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the thermoplastic casing.
 8. The deep fryer pump of claim 7 wherein the fasteners are cap screws.
 9. The deep fryer pump of claim 7 wherein the through bore of thermoplastic casing includes no bearings that engage the drive shaft.
 10. The deep fryer pump of claim 7 wherein the through bore of the thermoplastic casing and the drive shaft are sized so the through bore supports and provides a bearing function for the drive shaft without the use of an additional bearing.
 11. The deep fryer pump of claim 7 wherein the through bore comprises a distal end connected to the pump chamber and a proximal end connected to the proximal end of the thermoplastic casing, the proximal end of the through bore being recessed to accommodate a seal through which the drive shaft passes.
 12. The deep fryer pump of claim 7 wherein the distal end of thermoplastic casing comprises a groove that encircles the pump chamber for accommodating a seal that is sandwiched between the distal end of the thermoplastic casing and the thermoplastic head.
 13. A deep fryer pump, the pump consisting essentially of: a casing consisting essentially of a through bore for accommodating a drive shaft, a pump chamber for accommodating a drive gear and a driven gear, a recess connected to the pump chamber for accommodating a stationary pin, a proximal end coupled to a motor, a distal end coupled to a thermoplastic head, and a groove that encircles the pump chamber for accommodating a seal that is sandwiched between the distal end of the thermoplastic casing and the thermoplastic head, the gears enclosed in the pump chamber by the thermoplastic head, the stationary pin coupled to the driven gear, the drive shaft coupled to the drive gear, the thermoplastic head consisting essentially of a plate with a plurality of holes for accommodating fasteners that couple the thermoplastic head to the distal end of the thermoplastic casing, and the through bore comprises a distal end connected to the pump chamber and a proximal end connected to the proximal end of the thermoplastic casing, the proximal end of the through bore being recessed to accommodate a seal through which the drive shaft passes
 14. The deep fryer pump of claim 13 wherein the fasteners are cap screws.
 15. The deep fryer pump of claim 13 wherein the through bore of the thermoplastic casing and the drive shaft are sized so the through bore supports and provides a bearing function for the drive shaft without the use of an additional bearing.
 16. The deep fryer pump of claim 13 wherein the casing and head are fabricated from engineered thermoplastics.
 17. The deep fryer pump of claim 16 wherein the pump is listed for use as a deep fryer oil pump by NSF. 